This invention relates to thermal insulation used in high temperature aerospace vehicle applications. The new thermal insulating conformal blanket is constructed by incorporating an initially generally rigid batting material with surface layers fastened to provide a lower cost, reusable insulating device.
Use of thermal insulating devices is known in the aerospace industry. This subject has been extensively investigated under NASA direction, as is evidenced in U.S. Pat. No. 5,038,693. The patent discloses the investigation of various batting materials, surface layers, and threads for stitching the materials together. While these investigations have produced notable results in materials development, a thermal insulation blanket for replacement of high temperature ceramic tiles for thermal protection on aerodynamic surfaces has not been discovered.
A primary impediment to the development of a less expensive, as compared to ceramic tile, thermal blanket product is the necessity that the outer surface of any insulation be relatively smooth to avoid aerodynamic drag and associated aerodynamic heating. U.S. Pat. No. 5,626,951 discloses materials that may be useful in developing a thermal insulating blanket. However, as in the case of other stitched blanket designs, the problem of establishing a near net shape manufacturing process using existing materials is not solved. The batting in the prior art is not structured to easily manufacture a stitched blanket that inhibits the undesired resultant pillowing effect, as well as other surface roughness features thus precluding its use on high temperature aerodynamic surfaces.
As can be seen, there is a need for a manufacturable, reliable, and affordable thermal insulating conformal blanket for use in replacing expensive ceramic tiles used on aerospace vehicles as an example.
An improved thermal insulating conformal blanket structure and manufacturing process according to the present invention comprises a firm, rigid ceramic batting material having an outer and inner surface layer material which elements are joined by stitching.
In one aspect of the present invention, an insulating blanket device for use with aerospace vehicles comprises a batting formed from a ceramic fiber material such that the batting may be firm and generally rigid to inhibit pillowing during the processing of the blanket device. The batting may be covered on all sides with an outer insulating layer resistant to high temperature. The batting and insulating layers may be fastened together by sewing or stitching.
In another aspect of the invention, the insulation blanket device comprised of the batting, outer insulating layer and inner insulating layer may have the batting formed to a composite structure that may have a firmness factor sufficient to inhibit a pillowing effect after the stitching operation of not more than about 0.03 inch. The stitching may use an outer mold layer thread of ceramic fiber material to stitch through the outer insulating layer and the batting, and an inner mold layer thread of ceramic fiber material as the bobbin thread to engage the outer mold layer thread.
In yet another aspect of the invention, the insulation blanket device may be processed in a heat cleaning cycle process after the stitching operation to reduce dirt, organics, and debris. The outer insulating layer and an upper portion of the batting adjacent the outer insulating layer may be impregnated with ceramic coating material to form a high temperature composite surface.
In a further aspect of the invention, a method of manufacture of a thermal insulation conformal blanket comprises the steps of fabricating a batting from alumina fiber material to a firmness factor that may inhibit a pillowing effect during stitching to not more than about 0.03 inch. The batting may then be covered with an outer insulating layer formed of woven ceramic fiber material and an inner insulating layer formed of woven ceramic fiber material. The batting and insulating layers may then be stitched together using an outer mold layer thread resistant to high temperature damage to stitch through the outer insulating layer and the batting, and a lower temperature resistant inner mold layer thread as a bobbin thread to form an insulation blanket device. The insulation blanket device may then be heat treated to remove contaminants. Finally, the outer insulating layer and an upper portion of said batting adjacent the outer insulating layer may be impregnated with a ceramic coating to form a high temperature composite surface.
These and other features, aspects and advantages of the present invention will become better understood with reference to the following drawings, description and claims.